The invention pertains to a longitudinal seat adjustment, especially for the seats of motor vehicles, with two pairs of rails, spaced a certain distance apart, each pair consisting of two rails, namely, an upper rail belonging to the seat and a lower rail belonging to the floor of the motor vehicle, and with at least one spring-loaded, movable, plate-shaped locking part, which is supported on the upper rail and which, when in the locking position, prevents the upper rail from moving in the lower rail, where the lower rail has tooth-like openings, where the upper rail is provided with slot-like openings, and where the locking part carries tooth-like projections on its two opposing long sides, which can be moved by a spring into both the slit-like openings and into the tooth-like slots to assume the locking position. A similar form of this type of longitudinal seat adjustment device is described in the unpublished Patent Application No. 100 41 605.5 of Aug. 24, 2000.
It is a disadvantage of the known designs that, because of the ability of the upper rail and lower rail to move with respect to each other when they are in the locked position, they are not held precisely without play. If sufficient load is exerted on them, they can be easily moved back and forth. In spite of the relatively small distance thus traveled, the play between the rail""s continues to increase as a result of wear under the constant use and the constant load exerted on them by the user of the seat.
The task of the invention is therefore to design the longitudinal seat adjustment device of the type indicated above in such a way that the two rails, i.e., the lower rail and the upper rail, are held in place precisely with respect to each other when in the locked position and cannot be shifted. In addition, this holding-in-place without play is to be achieved with the smallest possible number of parts. This task is accomplished according to the invention in that the tooth-like projections of the locking part can be moved by a spring into the openings and slots in such a way that the first tooth-like projection contacts the edge area of a slot while another projection contacts the edge area of an opening. When in its locked position, the locking part thus holds the upper and lower rails without play, specifically as a result of an angular and/or vertical movement of the locking part. Because the position of the locking part is variable with respect to the rails, this movement allows two tooth-like projections to contact each rail. The locking part rests without play between the two rails.
In a special exemplary embodiment of the invention, the locking part supported on the upper rail is supported with freedom to tilt and/or to rotate, which ensures that the locking part, the upper rail, and the lower rail are held together without play; in this case, one end of the locking part contacts one of the rails, while the other end contacts the other rail. One projection engages in an opening, another one in a slot. The rails are thus no longer free to shift.
It is favorable for at least one tooth of the locking part, when executing a tilting motion, to contact the edge areas of one of the slit-like openings in the upper rail, while another tooth contacts the edge areas of a slot.
In a special exemplary embodiment of the invention, the openings and slots are designed with wedge-like shapes so that, upon engagement of the tooth-like projections, the spring, while rotating the locking part, can hold the edge areas without play between the two rails. It is advantageous for the first tooth-like projection of the locking part to be wider than the last tooth-like projection, and for an opening situated remotely from the first tooth of the locking part to be designed in the shape of a wedge, because, in an exemplary embodiment designed in this way, the edge areas of the slots and openings will be contacted when the locking part executes its tilting and/or rotating movement, and thus the rails will no longer have any freedom to move when in the locked position.